Induced muscle contraction through the application of electrical stimulation is well known to the prior art. An example of such a contraction is that induced in the heart by the well-known cardiac pacemaker. Other induced muscle contractions also have proven medically beneficial.
Some muscle dysfunctions and insufficiencies are not adequately or appropriately addressed by contraction inducing electrical stimulation. For example, the muscle tissue may not be adequately responsive to stimulation energy or may require too high an energy threshold for practical contraction inducement. In such instances, a surgical therapy would be a useful alternative, the replacement of non-functioning myocardial tissue with contractile tissue, for example. Ideally, such a tissue graft should have the potential for growth and differentiation and be autogenous so as to overcome the problems associated with tissue rejection. Another condition that could be addressed through a graft of contractile tissue is a congenitally hypoplastic heart, or a portion thereof. Numerous other examples of muscle contraction dysfunctions and insufficiencies that could be addressed by the grafting of contractile tissue will be apparent to those familiar with muscle physiology.
It is unlikely that a muscle graft, as described above, will contract in response to the same processes that induce a normal contraction in the surrounding tissue. Accordingly, it may be necessary to provide a system that will induce a contraction in the grafted tissue. Further, the tissues conveniently available may be of the wrong response type, the differentiation of muscle tissue between fast and slow--often referred to as fast twitch and slow twitch, respectively--being well known. For example, in a replacement of myocardial tissue or the surgical therapy for congenitally hypoplastic portions of the heart discussed above, it appears most convenient to use diaphragm tissue for the tissue graft. However, diaphragm muscle tissue is a fast muscle while myocardial tissue is a slow muscle. Thus, a diaphragm graft on the heart can be expected to fatigue if it retains its fast muscle character. Accordingly, in conjunction with providing a pacing system for a muscle graft, it is desirable that that system have the capability of conditioning the muscle graft to transform it to the desired muscle response type and/or maintain a desired muscle response type.